1. Field of the Invention
The present invention is directed toward a method for controlling a vehicle heating, ventilation, and air conditioning (HVAC) system.
2. Description of Related Art
In modern vehicles it is common to have an HVAC system for an occupant compartment (hereinafter “cabin”). The HVAC system provides warm and cool air to the cabin of the vehicle. Further, an HVAC control system allows occupants to select a set temperature for the cabin. Once the set temperature is selected, the HVAC control system provides conditioned air to adjust the climate of the cabin.
The conditioned air that is heated is typically provided to the cabin by passing outside air through a heater core before being discharged into the cabin. The conditioned air that is cooled is typically provided to the cabin by passing outside air through an evaporator before being discharged into the cabin. Many times, the HVAC control system includes a controller that automatically makes adjustments, based upon the set temperature, to raise or lower the temperature of the conditioned air.
For example, the position of an air mix door determines the amount of air that can flow through the heater core. The more air that flows through the heater core, the warmer the air in the cabin will become. Typically, the position of the air mix door is controlled by the controller. Usually, the controller determines the position of the air mix door by a calculation that includes several variables. For example, the temperature of the evaporator and the calculated outlet temperature are used in the calculation. Further, a predicted temperature of air leaving the heater core, which is based upon engine coolant temperature, is used.
However, it has been found that during cold outside air temperatures, the calculation used to determine the position of the air mix door and the related subsequent control of the air mix door, results in an under-heating of the cabin. It can be appreciated that this under-heating of the cabin is undesirable.
Therefore, there exists a need in the art for a method to better control the HVAC system so as to provide conditioned air that will properly adjust the cabin air to maximize occupant comfort.